As it is generally known, labelling machines are used to apply labels to containers or articles of all sort. Typically, for beverage bottles or vessels, two alternative techniques can be provided to attach the labels on the external surface of respective bottles. According to a first technique, the back surfaces of the labels (commonly called “roll labels”) are covered with glue and are stuck onto the external surfaces of the bottles. According to a second technique, after having placed tubular labels made of heat-shrinkable film (commonly called “sleeve labels”) around respective bottles, the tubular labels are heated to fit and adhere onto the bottles.
In particular, these tubular labels are obtained by:                cutting a web unwound from a supply roll into a plurality of rectangular or square labels;        bending each label in a cylindrical configuration such that the opposite vertical edges overlap one another; and        welding the overlapped edges of each cylindrical label.        
A particular type of labelling machine is known which serves to bend and weld labels in a tubular configuration and then to produce insertion of the bottles into the so formed tubular labels before the heating operation. This kind of machine basically comprises a carousel rotating about a vertical axis to define a circular path, along which it receives a succession of unlabelled bottles by a bottle input wheel and, then, a succession of rectangular or square labels by a label input wheel, produces application of the labels in a tubular configuration onto the respective bottles, and releases the labelled bottles to an output wheel.
More specifically, the carousel comprises a plurality of labelling units which are equally spaced along a peripheral edge of the carousel and are moved by the latter along the above-mentioned circular path.
Each labelling unit comprises a supporting assembly adapted to support the bottom wall of a relative bottle and an upper retainer adapted to cooperate with the top portion of such bottle, to hold it in a vertical position during the rotation of the carousel about its vertical axis.
Each supporting assembly comprises a vertical hollow supporting mount, secured to a horizontal plane of a rotary frame of the carousel; and a cylindrical receiving member, which engages the supporting mount in sliding and rotating manner with respect to its vertical axis, and is adapted to carry a relative bottle on its top surface and a relative label on its lateral surface.
The receiving members are displaced by a cam and tappet device between a raised position and a lowered position, while moving along the above mentioned circular path.
In the lowered position, the receiving member is fully retracted within the relative supporting mount, so that the top surface of each receiving member is flush with the top surface of the supporting mount. At the output wheel and at the bottle input wheel, each receiving member is located in its lowered position, so that the bottles are transferred onto and from the carousel along the same transfer horizontal plane.
In the raised position, each receiving member protrudes from a top surface of the relative supporting mount and is adapted to receive a relative label on its lateral surface from the label input wheel; in particular, the label is wrapped around the receiving member such that the opposite vertical edges of the label overlap one another. In order to produce this complete wrapping, the receiving member is rotated about its vertical axis during the transfer of the label from the label input wheel. The label is retained on the lateral surface of the receiving member by suction; for this purpose, at least a region of the lateral surface of the receiving member is provided with a plurality of holes, which are connected to a pneumatic suction device.
After having welded the overlapping edges of the tubular label, the suction is released and the receiving member is lowered, so as to produce the insertion of the relative bottle downwards inside the tubular label, therefore making the ensemble of the bottle and the surrounding label ready to be transferred to the output wheel.
The known labelling machines of this kind, working with the so-called “sleeve labels”, are not suitable to work also with the so-called “roll labels”, because the latter have to be stuck to the external surfaces of the bottles without providing vertically movable receiving members, i.e. without vertically moving the bottles. Indeed, in carousels provided to support and transfer bottles onto which labels are applied by means of glue, the supporting assemblies of the labelling units are simplified in comparison to the above described ones.
A need is felt to provide a single machine that can be configured by means of a relatively low number of operations to apply either the so-called “sleeve labels” or the so-called “roll labels”, without removing or changing components from all the labelling units of the carousel.